Metal surface treatment agent

ABSTRACT

The present invention relates to a metal surface treatment agent that characteristically contains (A) at least 1 vanadium compound and (B) at least one metal compound containing at least 1 metal selected from the group consisting of zirconium, titanium, molybdenum, tungsten, manganese, and cerium. The present invention also relates to a metal surface treatment method using the foregoing treatment agent and the corresponding surface-treated metals.  
     The present invention provides a metal surface treatment agent that does not contain chromium and that can be used to impart an excellent corrosion resistance and alkali resistance to metals. The present invention provides a metal surface treatment method that uses the foregoing treatment agent and also provides the corresponding surface-treated metals.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a metal surface treatment agent andmethod that can be used to form a chromium-free coating on the surfaceof metal sheet coil and metal formed articles and that impart to suchsurfaces an excellent corrosion resistance and excellent alkaliresistance. The invention also relates to the correspondingsurface-treated metals.

[0003] More particularly, this invention relates to a metal surfacetreatment agent and method that can be used to form a chromium-freecoating that imparts an excellent corrosion resistance and excellentalkali resistance to formed articles, castings, and sheet coil (forexample, automotive body elements and other automotive parts,construction materials, parts for household electrical appliances) ofzinciferous-plated steel sheet, steel sheet, or aluminiferous metal. Theinvention additionally relates to the corresponding surface-treatedmetals.

[0004] 2. Background Art

[0005] Metals such as zinciferous-plated steel sheet, steel sheet, andaluminiferous metals are susceptible to oxidation and corrosion byatmospheric oxygen, moisture, and the ions present in moisture. Oneknown method for inhibiting this corrosion comprises forming a chromatecoating on the metal surface by bringing the metal into contact with achromium-containing treatment bath, for example, a chromic acid chromateor phosphoric acid chromate bath.

[0006] While the coatings generated by these chromate treatments do tendto exhibit excellent corrosion resistance and excellent paint adherence,the treatment baths used in these treatments typically contain toxichexavalent chromium, which can impose substantial time, labor, and costburdens on wastewater treatment. Moreover, hexavalent chromium is alsopresent in the coatings produced by these treatments, which has ledbased on environmental and safety considerations to an ever increasingtendency to avoid the use of these coatings.

[0007] Methods that employ non-chromate (chromium-free) treatments bathsare known. For example, Japanese Laid Open (Kokai or Unexamined) PatentApplication Number Hei 7-278410 (278,410/1995) teaches a polymercomposition and a method for treating metal surfaces wherein the polymercomposition contains an acidic compound and a phenolic resin-typepolymer with a specific structure. An agent and method for treatingmetal surfaces are also disclosed in Japanese Laid Open (Kokai orUnexamined) Patent Application Number Hei 8-73775 (73,775/1996). Thisagent and method provide an excellent fingerprint resistance. The agentcontains at least 2 silane coupling agents having reactive functionalgroups with specific structures; these reactive functional groups aredifferent from each other but are capable of reacting with one other.Japanese Laid Open (Kokai or Unexamined) Patent Application Number Hei9-241576 (241,576/1997) discloses a method and agent for treating metalsurfaces wherein the agent contains a silane coupling agent with aspecific structure and a phenolic resin-type polymer with a specificstructure. Japanese Laid Open (Kokai or Unexamined) Patent ApplicationNumber Hei 10-1789 (1,789/1998) teaches an agent and method for treatingmetal surfaces and metal surfaces thereby treated. This agent contains aspecific polyvalent anion and an organic polymer, such as an epoxyresin, acrylic resin, or urethane resin, that contains at least 1nitrogen atom. Japanese Laid Open (Kokai or Unexamined) PatentApplication Number Hei 10-60233 (60,233/1998) teaches a treatment methodthat uses two rust preventives (1) and (2) and metals thereby treated.Rust preventive (1) contains a bisphenol A epoxy resin with a specificstructure, while rust preventive (2) contains phenolic resin and aspecific non-phenolic resin (e.g., polyester) in quantities that providea solids ratio of 4:1 to 1:4 upon mixing.

[0008] None of the metal surface treatments taught in these laid openpatent applications uses chromium, and, while they do offer theadvantage of a treatment bath free of hexavalent chromium, in each casethey produce coatings that exhibit a corrosion resistance inferior tothe corrosion resistance from chromate treatment. The coatings producedby these chromium-free treatments also suffer from an unacceptablefingerprint resistance and lubricity.

[0009] Japanese Laid Open (Kokai or Unexamined) Patent ApplicationNumber Hei 10-1789 teaches vanadic acid among the therein specifiedpolyvalent anions. However, vanadic acid, which is an oxyacid ofpentavalent vanadium, has a poor resistance to water and alkali. As aresult, when the treated metal is rinsed, and particularly when it isrinsed with alkali, the vanadic acid is eluted from the coating, whichresults in a major reduction in corrosion resistance. This laid openpatent application also teaches the post-treatment execution of a waterrinse and drying. Thus, while the problem of a chromium-containingwastewater is not present, the organics create the problem of aCOD-containing wastewater.

[0010] Inventions that use vanadium compounds as rust preventives arealso known. Japanese Laid Open (Kokai or Unexamined) Patent ApplicationNumber Hei 1-9229 (9,229/1990) teaches an antirust paint that contains afilm-forming resin, a phosphate ion source that releases phosphate ionin an ambient containing water and oxygen, and a vanadate ion sourcethat releases vanadate ion in an ambient containing water and oxygen.Japanese Granted Patent 2,795,710 teaches an antirust composition inwhich specific compounds are blended in specific proportions; thespecific compounds include (A) a vanadate ion source that releasesvanadate ion in specific concentrations in a water-based dispersion and(B) an organophosphonic acid capable of dissolution in specificconcentrations in a water-based dispersion. The vanadate ion source isadded to function as the antirusting pigment of these antirust paints,and when baked at high temperatures (600° C. and above) is converted toa pigment with an average particle size of several μm. The particles ofthis pigment do manifest an anticorrosion activity when present in paintfilms having a certain film thickness (several times the particle sizeof the pigment), but exhibit no anticorrosion activity at all in thethin films (no greater than several μm) encountered in the field ofmetal treatment. Another problem with these treatment agents is thatsettling occurs due to aggregation of the particles therein when thetreatment agent is allowed to stand.

[0011] Thus, no extant non-chromate metal surface treatment agent hasthe ability to form a coating that can simultaneously impart anexcellent corrosion resistance, an excellent alkali resistance, and anexcellent fingerprint resistance to metal surfaces.

SUMMARY OF THE INVENTION

[0012] The present invention remedies the herein above describedproblems associated with the prior art. An object of the presentinvention is to provide a metal surface treatment agent that does notcontain chromium and that can impart an excellent corrosion resistanceand excellent alkali resistance to metals. Additional objects of thepresent invention are to provide a metal surface treatment method thatuses this agent and metals whose surface has been treated using theinventive agent and method.

[0013] The present inventors have discovered that highlycorrosion-resistant, highly alkali-resistant coatings can be obtained bytreating metal surfaces with a surface treatment agent whose essentialcomponents are a vanadium compound and a particular type of metalcompound. This invention was achieved based on this discovery.

[0014] In specific terms, this invention relates to a metal surfacetreatment agent that characteristically contains: (A) at least 1vanadium compound and (B) a metal compound or compounds containing atleast 1 metal selected from the group consisting of zirconium, titanium,molybdenum, tungsten, manganese, and cerium.

[0015] In an embodiment preferred in order to obtain a better stabilityby the vanadium compound in the treatment agent and an improvedcorrosion resistance and alkali resistance by the produced film, theratio in vanadium compound (A) of vanadium ion in the trivalent andtetravalent oxidation states to the total vanadium (V³⁺+V⁴⁺)/V is in therange of 0.1 to 1.0.

[0016] In another preferred embodiment, the inventive metal surfacetreatment agent additionally contains (C) an organic compound thatcontains at least 1 functional group selected from the group consistingof hydroxyl groups, carbonyl groups, carboxyl groups, primary totertiary amino groups, amide groups, phosphoric acid groups, andphosphonic acid groups. The purpose of this embodiment is to reduce thepentavalent vanadium compound, when used, to the tetravalent ortrivalent oxidation state and/or to improve the stability of thevanadium compound in the inventive treatment bath.

[0017] In another embodiment preferred in order to improve the adherenceof the obtained coating, the inventive metal surface treatment agentadditionally contains (D) at least 1 etchant selected from the groupconsisting of inorganic acids, organic acids, and fluorine compounds.

[0018] The invention additionally relates to a method for treating metalsurfaces comprising treating a metal surface with any of the inventivemetal surface treatment agents described above, and drying by heating sothe temperature of the metal reaches 50 to 250° C.

[0019] The invention further relates to surface-treated metals that beara coating produced using the aforementioned inventive surface treatmentmethod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0020] The vanadium compound present in the metal surface treatmentagent of the present invention comprises at least 1 selection fromvanadium compounds in which the vanadium has a pentavalent, tetravalent,or trivalent oxidation state. Examples of suitable vanadium compoundsinclude, but are not necessarily limited to, pentavalent vanadiumcompounds such as vanadium pentoxide (V₂O₅), metavanadic acid (HVO₃),ammonium metavanadate, sodium metavanadate, and vanadium oxytrichloride(VOCl₃), and trivalent and tetravalent vanadium compounds such asvanadium trioxide (V₂O₃), vanadium dioxide (VO₂), vanadium oxysulfate(VOSO₄), vanadium oxyacetylacetonate (VO(OC(CH₃)═CHCOCH₃)₂), vanadiumacetylacetonate (V(OC(CH₃)═CHCOCH₃)₃), vanadium trichloride (VCl₃), andphosphovanadomolybdic acid {H₁₅—X(PV₁₂—xMoxO₄₀)·nH₂O(6<×<12, n<30)}.

[0021] Preferably, the treatment agent of the present invention containsa trivalent or tetravalent vanadium compound as the vanadium compound(A). More preferably, the ratio of vanadium ions in the trivalent andtetravalent oxidation states to the total vanadium (V³⁺+V⁴⁺)/V (V³⁺refers to the mass of the vanadium in the trivalent oxidation state, V⁴⁺refers to the mass of the vanadium in the tetravalent oxidation state,and V refers to the total mass of the vanadium) is in the range of 0.1to 1.0, even more preferably in the range of 0.2 to 1.0, and mostpreferably in the range of 0.4 to 1.0. When this ratio is below 0.1, thestability of the vanadium in the treatment agent can be poor and theultimately formed coating may have reduced corrosion resistance andalkali resistance.

[0022] Preferably, the ratio of vanadium ions in the pentavalentoxidation state (V⁵⁺) to the total vanadium is in the range of 0 to 0.9,even more preferably in the range of 0 to 0.8, and most preferably inthe range of 0 to 0.6.

[0023] One process for introducing a trivalent or tetravalent vanadiumcompound into the treatment agent of the present invention comprisesusing at least one of the trivalent or tetravalent vanadium compoundsdescribed above. Another suitable process comprises effecting apreliminary reduction of a pentavalent vanadium compound to a trivalentor tetravalent vanadium compound using a reducing agent. The reducingagent used for this purpose may be inorganic or organic but preferablyis organic. The use of the above-described compound (C) is particularlypreferred.

[0024] The component (B) present in the inventive metal surfacetreatment agent of the present invention comprises a metal compound orcompounds containing at least 1 metal selected from the group consistingof zirconium, titanium, molybdenum, tungsten, manganese, and cerium.Component (B) can preferably be an oxide or hydroxide of the specifiedmetals, a complex of these metals, or the salt of an inorganic ororganic acid. Suitable examples of metal compound (B) include, but arenot necessarily limited to, zirconyl nitrate ZrO(NO₃)₂, zirconylacetate, zirconyl sulfate, ammonium zirconyl carbonate(NH₄)₂(Zr(CO₃)₂(OH)₂), dizirconium acetate, titanyl sulfate TiOSO₄,titanium lactate, diisopropoxytitanium bisacetylacetone(C₅H₇O₂)₂Ti(OCH(CH₃)₂)₂, the reaction product of lactic acid andtitanium alkoxide, molybdic acid H₂MoO₄, ammonium molybdate, sodiummolybdate, molybdic acid compounds such as ammonium molybdophosphate(NH₄)₃(PO₄Mo₁₂O₃₆)·3H₂O and sodium molybdophosphateNa₃(PO₄·12MoO₃)·nH₂O, metatungstic acid H₆(H₂W₁₂O₄₀), ammoniummetatungstate (NH₄)₆(H₂W₁₂O₄₀), sodium metatungstate, paratungstic acidH₁₀(W₁₂O₄₆H₁₀), ammonium paratungstate, sodium paratungstate,permanganic acid HMnO₄, potassium permanganate, sodium permanganate,manganese dihydrogen phosphate Mn(H₂PO₄)₂, manganese nitrate Mn(NO₃)₂,manganese sulfate, manganese fluoride, manganese carbonate MnCO₃,manganese acetate, cerium acetate Ce(CH₃CO₂)₃, cerium nitrate, andcerium chloride.

[0025] The organic compound (C) present on an optional basis in themetal surface treatment agent of the present invention comprises anorganic compound that contains at least 1 functional group selected fromthe group consisting of hydroxyl groups, carbonyl groups, carboxylgroups, primary to tertiary amino groups, amide groups, phosphoric acidgroups, and phosphonic acid groups.

[0026] Suitable examples of organic compound (C) include, but are notnecessarily limited to, alcohols such as methanol, ethanol, isopropanol,and ethylene glycol; carbonyl compounds such as formaldehyde,acetaldehyde, furfural, acetylacetone, ethyl acetoacetate,dipivaloylmethane, and 3-methylpentanedione; organic acids such asformic acid, acetic acid, propionic acid, tartaric acid, ascorbic acid,gluconic acid, citric acid, and malic acid; amine compounds such astriethylamine, triethanolamine, ethylenediamine, pyridine, imidazole,pyrrole, morpholine, and piperazine; acid amide compounds such asformamide, acetamide, propionamide, and N-methylpropionamide; aminoacids such as glycine, alanine, proline, and glutamic acid;organophosphoric acids such as aminotri(methylenephosphonic acid),1-hydroxyethylidene-1,1′-diphosphonic acid,ethylenediaminetetra(methylenephosphonic acid), and phytic acid;monosaccharides such as glucose, mannose, and galactose;oligosaccharides such as maltose and sucrose; natural polysaccharidessuch as starch and cellulose; aromatic compounds such as tannic acid,humic acid, ligninsulfonic acid, and polyphenols; and synthetic polymerssuch as polyvinyl alcohol, polyethylene glycol, polyacrylic acid,polyacrylamide, polyethyleneimine, and water-soluble nylon.

[0027] The use of the organic compound (C) is preferred for the purposesof reducing pentavalent vanadium compound, when used, to the tetravalentor trivalent vanadium compound and/or improving the stability of thevanadium compound in the treatment bath of the present invention.

[0028] The organic compound (C) can be preliminarily mixed with thevanadium compound with heating (for example, at 40 to 100° C. for 5 to120 minutes) to give a mixture in which the reduction and stabilizationreactions have been thoroughly developed and the resulting mixture canthen be blended into the surface treatment agent. Alternatively, thesurface treatment agent in the form of a simple mixture can be coated onthe metal surface and reduction can be developed during the ensuingthermal drying step.

[0029] The etchant (D) present on an optional basis in the metal surfacetreatment agent of the present invention comprises at least 1 compoundselected from inorganic acids, organic acids, and fluorine compounds.

[0030] The optional etchant (D) is used to etch the basis metal duringapplication of the treatment agent or during the thermal drying step.Suitable examples of etchant (D) include, but are not necessarilylimited to, inorganic acids such as phosphoric acid, nitric acid, andsulfuric acid; organic acids such as formic acid and acetic acid; andfluorine compounds such as hydrofluoric acid, fluoboric acid HBF₄,fluosilicic acid H₂SiF₆, fluozirconic acid H₂ZrF₆, fluotitanic acidH₂TiF₆, stannous fluoride SnF₂, stannic fluoride SnF₄, ferrous fluoride,and ferric fluoride. Use of the etchant (D) is preferred for the purposeof improving the adherence of the ultimately obtained coating.

[0031] The content of the constituent component in the treatment agentof the present invention is preferably as follows: for the vanadiumcompound (A), preferably 1 to 100 g/L as vanadium and more preferably 2to 70 g/L as vanadium; for the metal compound (B), preferably 1 to 100g/L as the metal and more preferably 2 to 70 g/L as the metal. Thevanadium compound (A)/metal compound (B) mass ratio is preferably 1/9 to9/1 calculated on the metal and is more preferably 2/8 to 8/2 calculatedon the metal.

[0032] The organic compound (C) is preferably added at from 0.05 to 10mass parts and more preferably at from 0.1 to 5 mass parts, in each caseper 1 mass part pentavalent oxidation state vanadium in the vanadiumcompound. An addition in excess of that required for reduction ispreferred in order to stabilize the reduced material in the treatmentbath.

[0033] The etchant (D) is present preferably at 1 to 100 g/L and morepreferably at 2 to 70 g/L.

[0034] The treatment agent of the present invention may also contain, tohelp improve the adherence and corrosion resistance of the coating, ametal sol such as a water-dispersible silica sol and/or alumina sol orzirconia sol; a silane coupling agent such as an aminosilane,epoxysilane, or mercaptosilane; and/or a water-soluble orwater-dispersible resin such as polyacrylic acid, polyacrylamide, orpolyvinyl alcohol. When such a component is added, it is preferablyadded at from 5 to 40 mass % of the total nonvolatile component and morepreferably at from 10 to 30 mass % of the total nonvolatile component.

[0035] For the purposes of this invention, the total nonvolatilecomponent is the component remaining after the surface treatment agenthas been dried by heating for 2 hours at 110° C.

[0036] The solvent used in the surface treatment agent of the presentinvention preferably comprises mainly water, but may on an optionalbasis also contain a water-soluble organic solvent, e.g., an alcohol,ketone, or glycol ether, in order to help improve the dryingcharacteristics of the coating.

[0037] The surface treatment agent of the present invention may alsocontain, within a range that does not impair the essential features ofthe present invention or the properties of the coating of the presentinvention, additives such as surfactant, defoamer, leveling agent,germicide/bactericide, and colorant.

[0038] The surface treatment method of the present invention will now bedisscussed.

[0039] The nature of the pretreatment for the surface treatment of thepresent invention is not particularly critical. As a general matter,surface treatment in accordance with the present invention will bepreceded by cleaning with an alkaline or acidic degreaser, or hot water,or solvent, in order to remove any oils and contaminants present on thesubstrate. This can be followed on an optional basis by surfaceconditioning with acid or alkali. In a preferred embodiment, cleaning ofthe substrate surface is followed by rinsing with water so as to removeas much cleaning agent as possible from the substrate surface.

[0040] The treatment method of the present invention comprisesapplication of the inventive surface treatment agent to the metalsurface followed by drying by heating to 50 to 250° C.; however, thetechniques used for application and drying are not particularlycritical.

[0041] The following application techniques will typically be used: rollcoating, in which the treatment agent is applied to the substratesurface by transfer from a roll; broadcasting of the treatment agentover the substrate surface using, for example, a shower ring, followedby roll squeegee; dipping the substrate in a treatment bath; or sprayingthe treatment agent on the substrate. While the temperature of thetreatment bath again is not specifically restricted, the treatmenttemperature is preferably from 0 to 60° C. and is more preferably from 5to 40° C. given that the solvent for the treatment agent of the presentinvention comprises mainly water.

[0042] The drying process does not necessarily require heating, andphysical removal, for example, by air drying or air blowing, can bepursued. However, drying by the application of heat is preferred inorder to improve the film-forming performance and increase theadherence. The temperature in such cases is preferably 50 to 250° C. andmore preferably 60 to 220° C.

[0043] Coating deposition is preferably from 0.005 to 1.5 μm as the dryfilm thickness and more preferably from 0.01 to 1.0 μm as the dry filmthickness. Acceptable corrosion resistance and overcoat adherence arenot obtained at less than 0.005 μm, while deposition in excess of 1.5 μmruns the risk of producing cracks in the coating and a decline inadherence by the coating itself.

[0044] The formation of an organic polymer coating in a dry filmthickness of 0.3 to 3.0 μm on the coating formed from the surfacetreatment agent of the present invention, in addition to boosting thecorrosion resistance and alkali resistance of the metal workpiece, canimpart thereto fingerprint resistance, solvent resistance, and surfacelubricity.

[0045] A preferred method for establishing this organic polymer coatingcomprises application of an overcoating agent (Z) whose main componentis water-soluble or water-dispersible organic polymer, followed bydrying by heating at an attained substrate temperature of 50 to 250° C.The water-soluble or water-dispersible organic polymer used in theovercoating agent (Z) can be, for example, polymer as afforded by thepolymerization of addition-polymerizable unsaturated monomer, such asacrylic resins and polyolefin resins, as well as polymer as afforded bya condensation reaction, such as epoxy resins, urethane resins,polyester resins, polyamide resins, and phenolic resins. Theglass-transition temperature of the subject organic polymer ispreferably from 0 to 120° C. and more preferably is from 10 to 100° C. Aglass-transition temperature below 0° C. may result in a coating withpoor strength and hardness, while a glass-transition temperature inexcess of 120° C. may result in poor film-formability and pooradherence.

[0046] In addition to containing at least 1 selection from the foregoingorganic polymers, the overcoating agent may preferably containwater-dispersible silica in order to improve the toughness andfingerprint resistance of the coating. The addition of a water-borne waxmay also be preferred in order to improve the lubricity. The preferredcontents of the foregoing components are as follows: for the organicpolymer, 50 to 100 mass parts nonvolatile component per 100 mass partstotal nonvolatiles in the overcoating agent; for the water-dispersiblesilica, 0 to 40 mass parts nonvolatile component per 100 mass partstotal nonvolatiles in the overcoating agent; and for the water-bornewax, 0 to 30 mass parts nonvolatile component per 100 mass parts totalnonvolatiles in the ovecoating agent. A crosslinker capable ofcrosslinking the organic polymer may also be present.

[0047] In one embodiment of the invention, one or more water-soluble orwater-dispersible organic polymers of the type described herein abovemay be incorporated directly into the metal surface treatment agent asan additional component (E).

[0048] When coated on a metal substrate and dried thereon by heating,the surface treatment agent of the present invention reacts with thesurface of the metal substrate and forms a fine, dense, and passivecoating.

[0049] The manifestation of excellent corrosion resistance by thecoating produced by the surface treatment agent of the presentinvention, without wishing to be bound to any particular theory, isbelieved to be due to a delocalization of the corrosion electrons(potential leveling) and a barrier effect by the coating that checks thepermeation of oxygen, moisture, and ions. With respect to the vanadiumcompound (A) of the present invention, it is believed that a pentavalentvanadium compound occurs with the generation of an oxygen-bondedpolyvalent anion and is unable to generate an entirely acceptableperformance due to its poor water resistance and alkali resistance.However, a coating having improved water resistance and alkaliresistance can be formed using a treatment agent of the presentinvention that contains reduced tetravalent and/or trivalent vanadiumcompounds. The organic compound (C) is believed both to reduce thepentavalent vanadium compound and at the same time to chelate andstabilize the trivalent and/or tetravalent vanadium afforded byreduction in and present in the aqueous solution.

[0050] The use of an organic polymer-based overcoating on the inventivefilm can provide an additional and substantial boost in corrosionresistance due to a synergetic interaction with the barrier activity ofthe overcoating.

EXAMPLES

[0051] The present invention is explained in greater detail hereinbelowby working and comparative examples. The working examples that followare intended only as individual examples and should not be construed aslimiting the present invention. The procedures used to evaluate thetreated sheet samples prepared in the working and comparative examplesare also explained below.

[0052] 1. Substrates

[0053] A: electrogalvanized steel sheet (sheet thickness=0.8 mm)

[0054] B: hot-dip galvanized steel sheet (sheet thickness=0.8 mm)

[0055] C: 55% Al/Zn-plated steel sheet (sheet thickness=0.5 mm)

[0056] 2. Inventive treatment baths

[0057] (1) Treatment bath components

[0058] The vanadium compounds (A) used in the treatment baths were asfollows.

[0059] A1: ammonium metavanadate

[0060] A2: vanadium pentoxide

[0061] A3: vanadium trioxide

[0062] A4: vanadium oxyacetylacetonate

[0063] The metal compounds (B) used in the treatment baths were asfollows.

[0064] B1: ammonium molybdate

[0065] B2: ammonium metatungstate

[0066] B3: ammonium zirconium carbonate

[0067] B4: fluotitanic acid

[0068] B5: manganese carbonate

[0069] The organic compounds (C) used in the treatment baths were asfollows.

[0070] C1: L-ascorbic acid

[0071] C2: D-glucose

[0072] C3: glyoxal

[0073] The etchants (D) used in the treatment baths were as follows.

[0074] D1: HF

[0075] D2: H₂ZrF₆

[0076] D3: CH₃COOH

[0077] D4: H₂SiF₆

[0078] (2) Preparation of the treatment baths

[0079] Examples 1 through 7: The vanadium compound (A), metal compound(B), etchant (D), and deionized water were mixed and heated at 50° C.for 1 hour.

[0080] Examples 8 through 11: The vanadium compound (A) was first mixedinto the 5% aqueous solution of the organic compound (C) followed byheating for 30 minutes at 80 to 100° C. After subsequently cooling toroom temperature, the metal compound (B) and then the etchant (D) wereadded. The bath was finally brought to its prescribed concentration bythe addition of deionized water.

[0081] 3. Overcoating baths

[0082] The overcoating agents (Z) and treatment methods therewith aredescribed below.

[0083] Z1: a water-borne treatment bath containing 10% nonvolatilefraction comprising 100 mass parts as solids of a water-bornepolyurethane (SUPERFLEX 100 from Dai-ichi Kogyo Seiyaku Co., Ltd.), 20mass parts as silica of a water-borne silica (SNOWTEX C from NissanChemical Industries, Ltd.), and 10 mass parts as solids of a water-bornewax (CHEMIPEARL W900 from Mitsui Chemicals, Inc.).

[0084] Z2: a water-borne treatment bath containing 20% nonvolatilefraction comprising 10 mass parts as silica of a water-dispersiblesilica and 100 mass parts as solids of an ammonia-neutralizedwater-borne polymer (ethylene-acrylic acid copolymer withethylene/acrylic acid=80/20 and average molecular weight=approximately20,000).

[0085] 4. Treatment sequence

[0086] (1) Degreasing

[0087] The substrate was degreased with an alkaline degreaser (PALKLIN364S from Nihon Parkerizing Co., Ltd., 20 g/L bath, 60° C., 10-secondspray, spray pressure=50 kPa) and was then rinsed with water by sprayingfor 10 seconds.

[0088] (2) Coating with the treatment bath of the present invention anddrying

[0089] I: the treatment bath was applied with a #3 bar coater followedby drying at a sheet temperature of 80° C. using a convection oven.

[0090] II the treatment bath was applied with a #3 bar coater followedby drying at a sheet temperature of 120° C. using a convection oven.

[0091] (3) Coating with the overcoating treatment bath and drying

[0092] An overcoating bath as described above was bar-coated to adry-film thickness of about 1 μm on the coating already formed using thetreatment bath and method of the present invention. This was followed bydrying by heating at a sheet temperature of 100° C.

[0093] 5. Evaluation procedures

[0094] (1) Corrosion resistance

[0095] The corrosion resistance was determined by salt-spray testingbased on JIS Z-2371. After salt-spray exposure for 72 hours or 120hours, the area of white rust production was scored on the followingscale.

[0096] Evaluation scale:

[0097] area of white rust development

[0098] ++: less than 10%

[0099] +: less than 30% but at least 10%

[0100] Δ: less than 60% but at least 30%

[0101] x: at least 60%

[0102] (2) Alkali resistance

[0103] A bath was prepared containing 20 g/L of the alkaline degreaserPALKLIN 364S from Nihon Parkerizing Co., Ltd. The resulting aqueousdegreaser solution was adjusted to 60° C. and then sprayed for 30seconds on the already treated sheet. This was followed by rinsing withwater and drying at 80° C. The sheet was subsequently evaluated forcorrosion resistance using the conditions and methodology described in(1) above.

[0104] (3) Fingerprint resistance

[0105] A finger was pressed onto the surface of the treated sheetfollowed by evaluation by visual inspection of the status of theresidual fingerprint trace.

[0106] Evaluation scale:

[0107] ++: residual fingerprint trace entirely absent

[0108] +: very faint residual fingerprint trace

[0109] Δ: residual fingerprint trace present

[0110] x: distinct residual fingerprint trace present

[0111] (4) Solvent resistance

[0112] An ethanol-soaked gauze was wrapped around a silicone rubber cube(1 cm) and this was rubbed back-and-forth 10 times on the test surfaceunder 50,000 kPa.

[0113] Evaluation scale:

[0114] ++: coating exfoliation almost entirely absent

[0115] +: slight exfoliation of the coating occurred

[0116] Δ: moderate exfoliation of the coating occurred

[0117] x: the coating was entirely exfoliated with exposure of thesubstrate

[0118] The treatment bath compositions and treatment methods used in theworking and comparative examples are reported in Tables 1 and 2, whilethe evaluation results for the treated sheets are reported in Tables 3and 4. The results reported in Table 3 confirm an excellent corrosionresistance and alkali resistance for coatings produced from inventivetreatment agents (Examples 1 through 11) containing the herein specifiedvanadium compound (A) and metal compound (B). In contrast, a poorcorrosion resistance and poor alkali resistance were obtained inComparative Examples 1 through 3, which either did not contain thevanadium compound (A) or did not contain the metal compound (B).

[0119] Examples 12 through 22 concerned the additional execution of aresin overcoating (Z1 or Z2) on the films produced in Examples 1 through11. Examples 12 through 22 all gave an excellent corrosion resistanceand alkali resistance as well as an excellent fingerprint resistance andsolvent resistance. In contrast to this, a poor corrosion resistance andpoor alkali resistance were obtained in Comparative Examples 4 through6, which either did not contain the vanadium compound (A) or did notcontain the metal compound (B). TABLE 1 working and treatment bathcomposition in g/L comparative vanadium (V³⁺ + V⁴⁺)/ metal compoundetchant treatment examples substrate (A)* total V (B)* (D) methodExample 1 A A1 (7) 0.72 B1 (5) — I A3 (18) B4 (10) Example 2 A A1 (7)0.72 B1 (5) D2 (2) I A3 (18) B4 (10) Example 3 A A4 (3) 1.0 B4 (2) D2(2) I Example 4 B A2 (7.2) 0.28 B3 (10) D1 (10) II A3 (2.8) A1 (3) 0.5B2 (2) D2 (10) II Example 5 B A3 (1) B5 (5) A4 (2) Example 6 C A3 (5)1.0 B4 (10) D4 (1) I A4 (10) Example 7 A A1 (7) 0 B1 (5) D1 (2) I B4(10) Comparative A — — B1 (5) D1 (2) I Example 1 B4 (10) Comparative BA2 (7.2) 0.28 — — II Example 2 A3 (2.8)

[0120] TABLE 2 working and treatment bath composition in g/L comparativevanadium metal compound organic compound etchant treatment examplessubstrate (A)* (B)* (C) (D) method Example 8 A A1 (12) B1 (5) C1 (5) D1(2) I B4 (5) Example 9 B A (7.5) B2 (5) C2 (7.5) D3 (5) II Example 10 AA1 (15) B3 (15) C3 (15) D2 (5) II Example 11 C A1 (10) B4 (6) C1 (1) D4(10) I A2 (20) B5 (4) Comparative A At (12) — C1 (5) D1 (2) I Example 3

[0121] Example 12: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 1.

[0122] Example 13: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 2.

[0123] Example 14: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 3.

[0124] Example 15: Treatment with overcoating agent Z2 was carried outon film formed in accordance with Example 4.

[0125] Example 16: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 5.

[0126] Example 17: Treatment with overcoating agent Z2 was carried outon film formed in accordance with Example 6.

[0127] Example 18: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 7.

[0128] Example 19: Treatment with overcoating agent Z2 was carried outon film formed in accordance with Example 8.

[0129] Example 20: Treatment with overcoating agent Z1 was carried outon film formed in accordance with Example 9.

[0130] Example 21: Treatment with overcoating agent Z2 was carried outon film formed in accordance with Example 10.

[0131] Example 22: Treatment with overcoating agent Z2 was carried outon film formed in accordance with Example 11.

[0132] Comparative Example 4: Treatment with overcoating agent Z1 wascarried out on film formed in accordance with Comparative Example 1.

[0133] Comparative Example 5: Treatment with overcoating agent Z1 wascarried out on film formed in accordance with Comparative Example 2.

[0134] Comparative Example 6: Treatment with overcoating agent Z2 wascarried out on film formed in accordance with Comparative Example 3.TABLE 3 working and comparative corrosion resistance alkali resistanceexamples after SST for 48 hours after SST for 48 hours Example 1 + +Example 2 ++ ++ Example 3 + + Example 4 ++ + Example 5 ++ ++ Example 6++ ++ Example 7 + Δ Example 8 ++ ++ Example 9 ++ ++ Example 10 ++ ++Example 11 ++ ++ Comparative Example 1 Δ x Comparative Example 2 Δ xComparative Example 3 Δ x

[0135] TABLE 4 alkali corrosion resistance working and resistance afterSST comparative after SST for 120 for 120 fingerprint solvent exampleshours hours resistance resistance Example 12 +/++ +/++ + + Example 13 ++++ ++ ++ Example 14 ++ + + ++ Example 15 ++ ++ ++ ++ Example 16 ++ ++ ++++ Example 17 ++ ++ ++ ++ Example 18 + +/Δ ++ ++ Example 19 ++ ++ ++ ++Example 20 ++ ++ ++ ++ Example 21 ++ ++ ++ ++ Example 22 ++ ++ ++ ++Comparative Δ x + Δ Example 4 Comparative Δ x + Δ Example 5 ComparativeΔ x + Δ Example 6

Advantageous Effects of the Invention

[0136] The treatment agent of the present invention is a non-chromatetreatment agent that is free of toxic chromium compounds. The film orcoating formed from the inventive surface treatment agent exhibits acorrosion resistance that is as good as or better than the corrosionresistance of prior-art chromate coatings. As a consequence of thesefeatures, the inventive surface treatment agent, surface treatmentmethod, and surface-treated metals will have a very high commercial andindustrial utilization value.

[0137] While embodiments of the invention have been illustrated anddescribed, it is not intended that these embodiments illustrate anddescribe all possible forms of the invention. Rather, the words used inthe specification are words of description rather than limitation, andit is understood that various changes may be made without departing fromthe spirit and scope of the invention. Moreover, the terms “a” and “an”,as used herein, mean one of more unless clearly indicated to thecontrary, and the term “as the metal” means calculated based on theamount of the metal in a compound.

What is claimed:
 1. A metal surface treatment agent comprising: (A) atleast 1 vanadium compound; and (B) at least one metal compoundcontaining at least 1 metal selected from the group consisting ofzirconium, titanium, molybdenum, tungsten, manganese, and cerium.
 2. Themetal surface treatment agent of claim 1, wherein the ratio in thevanadium compound (A) of vanadium ions in the pentavalent oxidationstate to the total vanadium V⁵⁺/V is in the range of 0 to 0.6.
 3. Themetal surface treatment agent of claim 1 or 2, further comprising (C) anorganic compound that contains at least 1 functional group selected fromthe group consisting of hydroxyl groups, carbonyl groups, carboxylgroups, primary to tertiary amino groups, amide groups, phosphoric acidgroups, and phosphonic acid groups, wherein the organic compound (C) ispresent in an amount of 0.05 to 10 mass parts per 1 mass partpentavalent oxidation state vanadium in the vanadium compound.
 4. Themetal surface treatment agent of any of claims 1 to 3, furthercomprising (D) at least 1 etchant selected from the group consisting ofinorganic acids, organic acids, and fluorine compounds, wherein theetchant (D) is present in an amount of 1 to 100 g/l.
 5. The metalsurface treatment agent of any of claims 1 to 4, wherein the vanadiumcompound (A) is present in an amount of 1 to 100 g/l as vanadium and themetal compound (B) is present in an amount of 1 to 100 g/l as metal. 6.The metal surface treatment agent of any of claims 1 to 5, wherein thevanadium compound (A)/metal compound (B) mass ratio is 1/9 to 9/1calculated on the metal.
 7. The metal surface treatment agent of anyclaims 1-6, further comprising (E) a water-dispersible or water-solubleorganic polymer.
 8. A method for treating a metal surface comprising:treating the metal surface with a metal surface treatment agentaccording to any of claims 1 to 7; and drying by heating so thetemperature of the metal reaches 50 to 250° C.
 9. A surface-treatedmetal that bears a coating formed using the surface treatment method ofclaim
 8. 10. A surface-treated metal that bears a coating formed usingthe surface treatment agent of any of claims 1 to
 7. 11. Asurface-treated metal of claim 10 further comprising an organic polymercoating, wherein the organic polymer coating comprises awater-dispersible or water-soluble organic polymer having a glasstransition temperature of 0 to 120° C.